C提高_day03_玩转多级指针

#include <stdlib.h>
#include <string.h>
#include <stdio.h>


char **getMem51(int num)
{
    int i = 0;
    char **p2 = NULL;
    p2 = (char **)malloc(sizeof(char *) * num);
    if (p2 == NULL)
    {
        return NULL;
    }

    for (i=0; i<num; i++)
    {
        p2[i] = (char *)malloc(sizeof(char)  * 100  ); //char buf[100];
        sprintf(p2[i], "%d%d%d", i+1, i+1, i+1);
    }
    return p2;
}

int getMem52(char ***p3 , int num)
{
    int i = 0;
    char **tmp = NULL;

    if (p3 == NULL)  //判断p3 而不是*p3.  p3指向的内存空间可以是NULL 
    {
        return -1;
    }
    
    tmp = (char **)malloc(sizeof(char *) * num);
    if (tmp == NULL)
    {
        return NULL;
    }

    for (i=0; i<num; i++)
    {
        tmp[i] = (char *)malloc(sizeof(char)  * 100  ); //char buf[100];
        sprintf(tmp[i], "%d%d%d", i+1, i+1, i+1);
    }
    *p3 = tmp; 
    //1 2

    return 0;
}

void getMem52_Free(char ***p3 , int num)
{
    int i = 0;
    char **tmp = NULL;

    if (p3 == NULL)
    {
        return ;
    }
    tmp = *p3; 

    for (i=0; i<num; i++)
    {
        free(tmp[i]);
    }
    free(tmp);
     
    *p3 = NULL; //把实参赋值成null
}

void main()
{
    int i = 0, j = 0;
    char **p2 = NULL;
    int num = 5;

    //p2 = getMem51(num);

    getMem52(&p2, num);

    for (i=0; i<num; i++)
    {
        printf("%s 
", p2[i]);
    }

    getMem52_Free(&p2, num);
    printf("hello...
");
    system("pause");
    return ;
}